1. Field of the Invention
This application relates to waterproof expansion joints for railway bridges.
2. Background of the Related Art
Railway bridges are continually in a state of motion. Expansion and contraction caused by changes in thermal conditions, deflections caused by live loads, and longitudinal forces caused by railway traffic all combine to produce nearly continuous motion in the decks of railway bridges. The most common method of accommodating this movement, and the forces associated with it, is the deck joint. Deck joints—spaces between the girders that make up the deck of the bridge—allow the bridge to experience expansion, contraction, deflection, etc. without damage. Railway bridges are typically covered with ballast, however, requiring some method of sealing the deck joints to be incorporated into the bridge design in order to inhibit the ballast from falling through the deck joints and creating a potentially hazardous situation below the bridge. One method of inhibiting this leakage of ballast is by covering the deck joints with rigid ballast protection plates.
While accommodating the expansion, contraction, displacement, and other movements of bridge decks, deck joints may allow water to pass through, creating potentially hazardous situations under the bridge, including icicles. Ballast protection plates do not typically inhibit the leakage of water through the deck joint. Existing methods of waterproofing deck joints are designed with automobile bridges in mind. Such waterproof joints do not withstand the pressure of ballast and railways.
Therefore, there is a need for waterproof expansion joints that stand up to the stresses of railway bridges and the ballast associated with them while still providing adequate protection from water leakage. Such a waterproof expansion joint will provide the benefits of waterproofing the deck joints without substantially altering the manner in which railway bridges are constructed, for example with ballast protection plates having centering tabs coupled to their bottom face.